Unit 4 · Statistics and Probability
Four colours - what is the probability of yellow?
Lesson 6 of 8
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About this lesson
P(blue) = 0.2. Red = 2 × blue, so P(red) = 0.4. P(green) = 0.3. All four colours must sum to 1: P(yellow) = 1 − 0.2 − 0.4 − 0.3 = 0.1.
Chapters
0:00Introduction
0:21The Question
1:03Unlocking the red button probability
1:34Summing the known sample space
1:57Isolating the yellow remainder
2:31Exam strategy — the whole-number integer check
3:15Confirming the final option
Question
Jessica has blue, green, red and yellow buttons in a bag.
There are twice as many red buttons as blue buttons.
If she takes one button out of the bag without looking:
- the probability that it is blue is 0.2
- the probability that it is green is 0.3
What is the probability that Jessica takes out a yellow button?
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